Go Example

package main

type printer interface {
    printFile()
}

package main

import "fmt"

type epson struct {
}

func (p *epson) printFile() {
    fmt.Println("Printing by a EPSON Printer")
}

package main

import "fmt"

type hp struct {
}

func (p *hp) printFile() {
    fmt.Println("Printing by a HP Printer")
}

package main

type computer interface {
    print()
    setPrinter(printer)
}

package main

import "fmt"

type mac struct {
    printer printer
}

func (m *mac) print() {
    fmt.Println("Print request for mac")
    m.printer.printFile()
}

func (m *mac) setPrinter(p printer) {
    m.printer = p
}

package main

import "fmt"

type windows struct {
    printer printer
}

func (w *windows) print() {
    fmt.Println("Print request for windows")
    w.printer.printFile()
}

func (w *windows) setPrinter(p printer) {
    w.printer = p
}

package main

import "fmt"

func main() {

    hpPrinter := &hp{}
    epsonPrinter := &epson{}

    macComputer := &mac{}

    macComputer.setPrinter(hpPrinter)
    macComputer.print()
    fmt.Println()

    macComputer.setPrinter(epsonPrinter)
    macComputer.print()
    fmt.Println()

    winComputer := &windows{}

    winComputer.setPrinter(hpPrinter)
    winComputer.print()
    fmt.Println()

    winComputer.setPrinter(epsonPrinter)
    winComputer.print()
    fmt.Println()
}

Print request for mac
Printing by a HP Printer

Print request for mac
Printing by a EPSON Printer

Print request for windows
Printing by a HP Printer

Print request for windows